Integer type would work fine.
The SAP Help example uses two counters in WAIT UNTIL condition.
WAIT UNTIL RCV_JOBS >= SND_JOBS UP TO '1' SECONDS.
While using gv_active, statement would be something like this.
WAIT UNTIL gv_active = 0 UP TO '1' SECONDS.
So, gv_active is essentially the difference between rcv_jobs and snd_jobs.